Source:

Response:

The amino acids that are used in life, like most other aspects of
living things, are very likely not the product of chance. Instead, they
likely resulted from a selection process. A simple peptide replicator
can amplify the proportion of a single handedness in an initially
random mixture of left- and right-handed fragments (Saghatelian et al.
2001; TSRI 2001). Self-assemblies on two-dimensional surfaces can also
amplify a single handedness (Zepik et al. 2002). Serine forms stable
clusters of a single handedness which can select other amino acids of
like handedness by subtituting them for serine; these clusters also
incorporate other biologically important molecules such as
glyceraldehyde, glucose, and phosphoric acid (Takats et al. 2003). An
excess of handedness in one kind of amino acid catalyzes the handedness
of other organic products, such as threose, which may have figured
prominently in proto-life (Pizzarello and Weber 2004).

Amino acids found in meteorites from space, which must have formed
abiotically, also show significantly more of the left-handed variety,
perhaps from circularly polarized UV light in the early solar system
(Engel and Macko 1997; Cronin and Pizzarello 1999). The weak nuclear
force, responsible for beta decay, produces only electrons with
left-handed spin, and chemicals exposed to these electrons are far more
likely to form left-handed crystals (Service 1999). Such mechanisms
might also have been responsible for the prevalence of left-handed
amino acids on earth.

The first self-replicator may have had eight or fewer types of amino
acids (Cavalier-Smith 2001). It is not all that unlikely that the same
handedness might occur so few times by chance, especially if one of the
amino acids was glycine, which has no handedness.

Links:

References:

Cavalier-Smith T. 2001. Obcells as proto-organisms: membrane
heredity, lithophosphorylation, and the origins of the genetic code,
the first cells, and photosynthesis. Journal of Molecular Evolution
53: 555-595.